In recent decades, the ruthless Casalesi clan of the Camorra mafia has earned billions of euros by burying more than 150,000 cubic metres of toxic waste in the countryside north of Naples.

So last Thursday night, when 90 carabinieri paramilitary police officers surrounded several apartment buildings in Caserta, the provincial capital, many residents thought an anti-mafia blitz was under way. The targets were in fact immigrants, under scrutiny for sanitary inspections of their homes.

It is part of a trend since Matteo Salvini of the far-right League became interior minister in June 2018. Senator Pietro Grasso, a member of the national anti-mafia commission and former prosecutor responsible for the 2006 arrest of the Sicilian mafia boss Bernardo Provenzano, said: “Unfortunately, the Italian government […] is prioritising immigration, making people believe it is an emergency, rather than fighting the real problems, such as the mafia. Meanwhile, the bosses are getting richer and richer.”

On Sunday, Salvini announced the interior ministry would review spending on police protection for men and women under threat from the mafia, declaring “some people have been under police escort for too long”.

In Catania, the eastern Sicilian stronghold of the powerful Santapaola clan, prosecutors are investigating NGO rescue boats, one of which was ordered to be seized in November after fears that discarded clothes worn by people arriving from Libya could have been contaminated with HIV.

In Riace, part of Reggio Calabria, from where the feared ‘Ndrangheta is thought to control much of Europe’s cocaine trade, Mimmo Lucano, an anti-mafia mayor who revitalised his community by welcoming asylum seekers, has been under investigation since October on suspicion of aiding illegal immigration. Lucano has had repeated death threats from mafiosi, who also poisoned two of his dogs.

In the past eight months, nearly 250 of Salvini’s tweets have addressed immigration, compared with 60 about organised crime.

Nicola Gratteri, one of Italy’s most respected anti-mafia prosecutors, said: “I’ve heard him [Salvini] talking about immigration a lot. Haven’t heard him talking about the mafia yet.” When Salvini has tweeted about organised crime, for example the arrests in December of 90 people in Europe and South America accused of links to the ‘Ndrangheta, it has often concerned investigations that began before his tenure.

Migrants wait to disembark in the Sicilian harbour of Catania, Italy, May 2018. Photograph: Guglielmo Mangiapane/Reuters

Arrivals to Italy have decreased by more than 80% since their peak. Thousands of police officers have conducted searches and inspections, and hundreds of people have been forcibly removed from welcome centres. Many of them are now homeless.

The evictions followed the approval of the “Salvini decree”, which removed humanitarian protections for those not eligible for refugee status and suspended the asylum application process for individuals considered “socially dangerous”.

Claudio Fava, the head of Sicily’s anti-mafia commission, whose father was murdered by the mafia in 1984, said: “The new security decree is a mirror of Salvini’s propaganda.

“The law addresses almost exclusively immigration, but a security decree should also be concerned with the mafia, which is clearly not a priority for Salvini. The only element in the decree that mentions the mafia regards the seizure of property.”

The Salvini decree established that villas confiscated from mafiosi would be auctioned off publicly after a certain time. Experts have questioned this, citing the likelihood that properties could be purchased by citizens acting as stand-ins for mafia bosses.

It feels as though the Italian mafias no longer make headlines, but others do. The interior ministry has carried out a ferocious campaign against what Salvini has described as a worse menace – the mysterious Nigerian mafia. In recent months, magistrates have arrested numerous individuals within the Nigerian community on suspicion of belonging to mafia clans.

Many investigators point out the Nigerian clans are subordinate to the Italian mafias, but Salvini and his supporters have been swift in justifying anti-immigration policies in the face of what they describe as an “invasion” of alleged African mafia bosses, which has risked aggravating racial prejudice.

The linking of migrant communities and organised crime has echoes of the past in Italy. Between 1880 and 1915, 4 million Italians reached the US, a small minority of whom were tied to the mafia, the largest criminal organisation in the world.

Mario Del Pero, a professor of international history at Sciences Po, said: “The anti-Italian prejudice, or rather ‘Italophobia’, was very strong in the United States. Its origins ranged from widespread hostility against the Catholic church to labelling Italians as criminals. Restrictive laws passed in 1921 and 1924 were written precisely to keep Italians out.”

In Caserta, the parallels are not lost. Moses, 34, who is from Nigeria and had his home searched by police, said: “[It is] the same sort of prejudice that migrants are facing in Italy more than 100 years later. History repeats itself, in this country more than anywhere else.”